WO2006021082A1 - Appareil de coulage de mousse métallique et procédés idoines - Google Patents

Appareil de coulage de mousse métallique et procédés idoines Download PDF

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Publication number
WO2006021082A1
WO2006021082A1 PCT/CA2005/001278 CA2005001278W WO2006021082A1 WO 2006021082 A1 WO2006021082 A1 WO 2006021082A1 CA 2005001278 W CA2005001278 W CA 2005001278W WO 2006021082 A1 WO2006021082 A1 WO 2006021082A1
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WO
WIPO (PCT)
Prior art keywords
molten metal
mould
crucible
chamber
foam
Prior art date
Application number
PCT/CA2005/001278
Other languages
English (en)
Other versions
WO2006021082B1 (fr
Inventor
James Killingbeck
Scott Nichol
Roger Seucharan
Richard Gordon Manley
Mark Morita
Original Assignee
Cymat Corp.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cymat Corp. filed Critical Cymat Corp.
Publication of WO2006021082A1 publication Critical patent/WO2006021082A1/fr
Publication of WO2006021082B1 publication Critical patent/WO2006021082B1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D18/00—Pressure casting; Vacuum casting
    • B22D18/06—Vacuum casting, i.e. making use of vacuum to fill the mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D18/00—Pressure casting; Vacuum casting
    • B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D25/00—Special casting characterised by the nature of the product
    • B22D25/005—Casting metal foams

Definitions

  • This invention relates to a process and apparatus for casting of metal foam articles. More particularly, the invention relates to an improved foam casting apparatus and method wherein the foaming nozzle is maintained above the level of the molten metal. Further, the invention relates to an improved foam casting apparatus and method wherein the foaming chamber is separated from the molten metal supply.
  • Lightweight foamed metal articles are of considerable interest to various industries, such as the automotive industry, due to their high strength to weight ratio.
  • such articles are formed by generating a gas within a bath or furnace or crucible containing a molten metal and allowing the gas to foam the molten metal.
  • the foam comprises a plurality of closed cells containing the gas with the walls of the cells formed of the metal.
  • the foam can be collected and formed into shaped articles or slabs and cooled to solidify.
  • the foaming gas can be generated by means of gas generating particles added to the molten metal (in a process commonly referred to as "in-situ foaming") or by introduction of the gas into the molten metal through a port or nozzle.
  • additives to the molten metal to reinforce the walls of the cells formed during the foaming process and prevent cells from coalescing or otherwise collapsing.
  • These additives generally comprise particles of, for example, refractory materials, silicon carbide (SiC) and other such materials as known in the art.
  • nozzles each having one or more openings through which a gas (such as air, nitrogen, or any other gas) is passed.
  • the nozzles are commonly positioned under the liquid level of the molten metal so that the gas is introduced directly into the molten metal to form bubbles.
  • the bubbles can then be collected, as a foam, on the surface of the melt.
  • the foam can be formed into a slab or directed into a mould (having a mould cavity in the three dimensional shape of a desired article) where it is cooled and hardened to form the desired foam article.
  • the present invention provides an apparatus and method for generating a metal foam.
  • the invention provides an apparatus for generating a metal foam wherein a gas injection nozzle is provided above the liquid level of the molten metal and wherein the apparatus includes a means of raising the level of the molten metal above the nozzle when foaming is required.
  • the invention provides an apparatus for generating a metal foam by introduction of a gas without an agitator.
  • the invention provides an apparatus for generating a metal foam that is modular in design.
  • the invention provides an apparatus for casting a metal foam article from a foam of a molten metal, the apparatus comprising:
  • the mould includes at least one mould cavity having the shape of the article and an opening for fluid communication between the crucible and the cavity;
  • a flow generating means for causing the molten metal to flow from the crucible to the mould, whereby the molten metal level in the crucible is varied from a first level below the gas injection nozzle to a second level above the gas injection nozzle.
  • the invention provides a method of casting a metal foam article from a foam of a molten metal comprising: a) providing a crucible containing the molten metal; b) providing a mould having a mould cavity having the shape of the article, the mould being located above the crucible and the mould cavity having an opening into the crucible for fluid communication therewith; c) providing a gas injection nozzle below the mould cavity opening; d) maintaining the level of the molten metal below the gas injection nozzle; e) raising the level of the molten metal above the gas injection nozzle; f) injecting gas through the gas injection nozzle to generate a foam of the molten metal; g) directing the foam into the mould cavity; h) filling the mould cavity with the foam and allowing the foam to cool; i) returning the level of the molten metal level to below the gas injection nozzle; j) removing the formed article from the mould cavity. [0015] In a further aspect, the invention provides an
  • the mould includes at least one mould cavity having the shape of the article and an opening for fluid communication between the crucible and the cavity;
  • a flow generating means for causing the molten metal to flow from the crucible to the mould; wherein the crucible and mould are releasably connected together.
  • Figure 1 is a cross sectional elevation of a foam casting apparatus according to an embodiment of the invention.
  • FIGS 2 to 5 illustrate various stages during the process of using the apparatus of
  • Figure 6 is cross sectional elevation of another embodiment of the apparatus of
  • Figure 7 is a cross sectional elevation of a foam casting apparatus according to another embodiment of the invention.
  • FIGS 8 to 11 illustrate various stages during the process of using the apparatus of Figure 7.
  • Figure 12 is a cross sectional elevation of an apparatus having modular components.
  • Figure 13 is a cross sectional elevation of a variation of the apparatus of Figure
  • Figures 14 to 16 are cross sectional elevations of another aspect of the apparatus of the invention.
  • Figure 17 is a plan view of an apparatus incorporating multiple gas discharge nozzles.
  • Figure 18 is a schematic cross sectional elevation of the apparatus of the invention incorporating pumps to cause flow of molten metal.
  • Figure 19 is a schematic cross sectional elevation of the apparatus of the invention incorporating a transfer channel for the generated foam
  • FIG. 1 illustrates an apparatus according to one embodiment of the invention.
  • the apparatus includes a crucible 10 containing a molten metal 12.
  • the molten metal may, for example, comprise molten aluminum, although other metals or combinations of metals will be apparent to persons skilled in the art.
  • stabilizing particles may comprise, for example, refractory particles, SiC particles or any other material as known in the art. It will be understood that the term "molten metal" as used herein will include a molten MMC.
  • the crucible 10 is divided into two chambers or partitions, 14 and 16, by means of a divider 18.
  • the purpose for the division of crucible will be discussed below.
  • the chambers 14 and 16 are preferably maintained in fluid communication with each other by means of an opening or channel 19, thereby permitting molten metal 12 to freely flow between both chambers.
  • the crucible 10 comprises a heat resistant vessel with walls that are capable of withstanding the temperatures required to contain a molten metal.
  • the crucible may also be referred to in the art as a furnace.
  • the crucible 10 is heated by means known in the art to maintain the molten metal 12 in the liquid state.
  • the crucible 10 may be provided with heating elements or be contained within a furnace in order to maintain the interior of the crucible at the desired temperature. It will be understood that the crucible and all associated components are made from materials that are capable of withstanding the temperatures required to maintain the molten metal in the liquid state.
  • the crucible 10 may be attached to a reservoir 20 containing additional molten metal to supplement the crucible.
  • the reservoir 20 and the crucible 10 may be in fluid communication through a conduit 22, which may be provided with a valve so that molten metal can be provided only upon demand, as it is depleted from the crucible.
  • the flow of molten metal such as from the reservoir 20 to the crucible 10 may be controlled by a variety of means.
  • the flow may be controlled by establishing a pressure differential between the reservoir and the crucible by applying pressure and/or a vacuum to one or both components.
  • the reservoir 20 may also be provided with a flared opening 21 to facilitate filling of the reservoir with the molten metal.
  • the crucible 10 may be provided with optional mixers or impellers in one or both chambers or partitions 14 and 16, as shown as 24 and 25, respectively.
  • Figures 1 to 6 show mixers in both chambers.
  • the mixers 24 and 25 may be used to ensure adequate mixing of the molten metal and to ensure that any stabilizing particles added to the molten metal are evenly distributed.
  • the mixers 24 and 25 are driven, respectively, by motors 26 and 27 as known in the art.
  • the chambers 14 and 16 serve as pressurizing and foaming chambers, respectively.
  • the pressurizing chamber 14 is provided with a gas introduction port 28 connected to a source of pressurized gas (not shown).
  • the gas may comprise air, nitrogen or any other gas as will be apparent to persons skilled in the art.
  • the port 28 is also provided with a valve 30 to control the direction of gas passing through the port 28.
  • the crucible 10 is pressurized by injecting a gas into the pressurizing chamber 14.
  • the port 28 is provided generally at the top of the chamber so that the gas is introduced above the liquid level of the molten metal 12. In this manner, the pressure within the chamber 14 is increased, thereby forcing the molten metal contained therein into the neighboring foaming chamber 16, via the channel 19.
  • the foaming chamber 16 is provided on its upper end with an opening or channel 32 that opens into a mould cavity 34 of a mould 36.
  • the mould cavity 34 is designed to have the three dimensional shape of an article to be formed. It will be appreciated that the method and apparatus of the present invention can be used to form various articles as known in the art.
  • the mould 36 is, in one aspect, provided in two halves 38 and 40. Various other configurations of the mould will be apparent to persons skilled in the art.
  • the sections 38 and 40 of the mould may optionally be connected to pistons 42 and 44, which assist in opening and closing the mould.
  • Actuators 46 and 48 may optionally be provided to drive the pistons 42 and 44 respectively to facilitate the opening and closing of the mould 40.
  • the entrance 33 to the mould cavity 34 may include an upwardly and outwardly flared inner wall 35 such that the entrance 33 has a lower cross sectional area than the remainder of the cavity.
  • the present inventors have found that such tapered opening to the mould cavity prevents a thick "skin" from forming at the bottom of the foamed article. It will be understood that the tapered wall 33 is optionally provided on the apparatus.
  • the foaming chamber 16 may optionally be provided with a generally conical hood 50 for tunneling or directing the molten metal or metal foam into the mould cavity 34 (as will be discussed further).
  • the foaming chamber 16 is also provided with a gas discharge nozzle 52.
  • the nozzle 52 is, in one aspect, connected to and driven by a motor 54, which rotates the nozzle.
  • a drive shaft 51 connects the nozzle 52 to the motor 54.
  • the nozzle 52 is also connected to a gas source 56, which supplies the nozzle 52 with a gas for generating a metal foam from the molten metal as will be described below.
  • the drive shaft 51 may be hollow and serve as a conduit for the gas supplied to the nozzle 52.
  • the gas may comprise air or nitrogen or any other gas as will be apparent to persons skilled in the art. It will be appreciated that the gas supply for the nozzle 52 may be the same as the source for the port 28.
  • the nozzle 52 may, as known in the art, comprise a porous plug that allows passage of the gas but inhibits entry of the molten metal, or may comprise any other form of nozzle as will be apparent to persons skilled in the art. Further, as described above, in one aspect, the nozzle of the invention is rotated so as to serve as a mixer. In other aspects, rotation of the nozzle may not be necessary. A seal 53 is preferably provided around the shaft of the nozzle 52 to prevent leakage of molten metal. A similar seal would preferably be provided for each of the mixers 24 and 25. Seals of this type are known in the art. [0038] In another aspect, the nozzle 52 may simply serve to inject the foaming gas and need not be rotated.
  • Figure 1 illustrates the starting position of the process wherein no pressure is applied to the pressurizing chamber 14 thereby resulting in the levels of the molten metal 12 to equilibrate.
  • the equilibrium level of the molten metal in the foaming chamber 16 is preferably retained below the gas discharge nozzle 52.
  • the nozzle is not wetted by the molten metal 12 when no foaming is required. In the result, the nozzle is prevented from being clogged with the molten metal thereby removing the need to continuously expel gas through the nozzle as discussed above.
  • Figure 2 illustrates the second step in the process of the invention wherein the chamber 14 is pressurized by forcing the pressurizing gas to enter through the gas port 28. Under such pressure, the molten metal 12 in the pressurizing chamber 14 is forced, as shown by the arrows, into the foaming chamber 16 thereby raising the liquid level in chamber 14 as shown in Figure 2. As also shown in Figure 2, the level of the molten metal is raised until the molten metal fills the mould cavity 34. As discussed above, the hood 50, when provided in the foaming chamber 16 (as with one embodiment of the invention), serves to guide the molten metal into the mould cavity 34.
  • vents are generally known in casting equipment.
  • the vent on the mould may simply comprise a hole that is plugged once the molten metal 12 fills the mould cavity. The plugging occurs when the molten metal fills the vent hole and freezes.
  • the vent hole (or holes) will be provided at the apex of the mould cavity so that plugging of the hole occurs after the air in the mould cavity is evacuated.
  • Figure 3 illustrates the next step in the process wherein, once the mould cavity is filled with the molten metal, the gas supply is to the gas discharge nozzle 52 in the foaming chamber 16 is switched on.
  • the supply of gas to the nozzle 52 initiates foaming of the molten metal as is known in the art, wherein bubbles of the gas surrounded by a film of the molten metal are created.
  • bubbles of the foam are generated, they rise through the molten metal due to the relatively lower density as compared to the molten metal.
  • the bubbles rise they are guided by the hood 50 into the mould cavity 34.
  • the gas discharge nozzle is positioned directly beneath the channel 32 to the mould cavity 34.
  • the rising foam displaces the molten metal within the mould cavity and occupies the space vacated by same, as shown in Figure 3. During this process, the pressure within the pressurizing chamber 14 is maintained.
  • the time span between filling of the mould cavity 34 with the molten metal and the initiation of the gas discharge through nozzle 52 is relatively short so as to prevent the nozzle from becoming clogged and to prevent the molten metal from freezing (i.e. solidifying) in the mould.
  • the specific time span will depend, inter alia, on the pressure supplied to the pressurization chamber 14, the viscosity of the molten metal, the temperature of the molten metal, the insulative capacity of the mould, and the volume of the mould cavity.
  • the foaming operation is continued until the mould cavity 34 is completely filled with the metal foam 58. At this point, the mould is allowed to cool, thereby solidifying the foam within the mould cavity 34. It will be understood by persons skilled in the art that foam will solidify faster than the liquid molten metal due to the lower heat capacity of the foam. As such, solidification of the foam within the mould cavity can be completed without any significant solidification of the liquid molten metal within the crucible 10 or the channel 32.
  • the mould can optionally be provided with a cooling means (not shown) such as a cooling coil or the like as known in the art.
  • the time required for cooling the foam in the mould will depend on a number of factors such as the volume of the mould cavity (i.e. the size of the article being formed), the ambient temperature, and the thickness of the mould walls.
  • Cooling of the foam 58 in the mould cavity 34 is continued until the foam is sufficiently hardened and does not leak or drip back into the crucible 10.
  • the foaming gas supply can be turned off and the pressure in the pressurizing chamber released. Depressurizing of the chamber 14 is achieved by opening the valve 30 thereby releasing the pressurizing gas through the port 28.
  • the liquid levels of the molten metal 12 in the two chambers 14 and 16 are again equilibrated, as shown in Figure 5, and the liquid level in the foaming chamber 16 is returned to a level below the nozzle 52.
  • the service life of the nozzle may also be extended by reducing the time that the nozzle is exposed to the molten metal.
  • Another advantage of the present invention relates to the positioning of the foaming nozzle 52 close to the channel 32 of the mould cavity 34.
  • the bubbles that are formed when the gas is introduced through the nozzle 52 have a short distance to travel to reach the mould cavity. This reduces the travel time of the bubbles through the molten metal, as required with prior art methods (where nozzles are positioned at the base of the crucible), and therefore reduces potential damage to the bubbles. Such damage includes collapse or coalescence of the bubbles, which may reduce the quality of the foam
  • the mould 36 may be opened by separating mould halves 38 and 40. As mentioned above, this may be achieved with pistons 42 and 44 connected to each of the mould halves 38 and 40, respectively. Once the mould is opened, the formed foam article is removed and the mould 36 is again closed, thereby returning the system to the position shown in Figure 1. The process can then be repeated.
  • a molten metal reservoir 20 may optionally be provided to replenish molten metal in the crucible 10 as it is used.
  • the provision of such a reservoir serves to reduce the time required in shutting down arid re-filling the crucible 10 as the volume of the molten metal is reduce during production of the foam articles.
  • the reservoir 20 may be connected to the crucible 10 by means of a port or conduit 22. It will be understood that the operation of the apparatus can be automated so that, for example, replenishing of the molten metal from the reservoir (if provided) can be conducted while the formed article is being removed from the mould.
  • the port between the reservoir 20 and the pressurizing chamber 14 may be replaced with an open channel 23, which permits molten metal to freely flow between the reservoir 20 and the chamber 14.
  • the reservoir will be of such a size as to allow the molten metal level there-within to rise to at least the height of the top of the mould cavity 34.
  • Such an arrangement permits the liquid levels in both the reservoir 20 and the foaming chamber 16 to rise simultaneously as the pressure within the pressurizing chamber 14 is increased (as discussed above). This is required since, in the embodiment illustrated in Figure 6, the molten metal in both the reservoir 20 and the foaming chamber 16 is permitted to freely flow in and out of the pressurizing chamber 14.
  • the level of the molten metal will rise equally in both the reservoir 20 and the foaming chamber and mould.
  • the height of the reservoir 20 should be at least as high as the top of the mould cavity (that is, the height to which the molten metal rises in the mould) in order to prevent the molten metal from spilling out of the reservoir.
  • this arrangement of the reservoir allows for direct 1 monitoring of the filling of the mould cavity by molten metal. In other words, by monitoring the level of the molten metal in the reservoir 20, it is possible to determine when the molten metal rises to fill the mould.
  • the invention permits the use of monitoring equipment (not shown) to monitor the height of the molten metal in the reservoir and to signal when the mould is filled.
  • monitoring equipment can be electronically connected to the pumping apparatus used to provide gas to the nozzle 52 thereby allowing automation of the foaming process. That is, the gas supply to the nozzle 52 can be automatically commenced when the monitoring equipment senses that the height of the molten metal in the reservoir 20 has risen to the height of the top of the mould cavity, signaling that the mould has been filled with molten metal.
  • the time between filling of the mould with molten metal and commencement of the foaming step should preferably be minimized.
  • the reservoir may be provided with a sensor (not shown) for monitoring and/or measuring the liquid level of the molten metal with such sensor being connected to a processor (not shown).
  • the processor may be included in a computer system.
  • the processor may also be programmed with the necessary instructions to be executed depending upon the level of molten metal.
  • the processor may be programmed to switch the gas supply to the gas injection nozzle on or off depending upon the sensed level of the molten metal.
  • the pressurizing chamber 14 and/or the foaming chamber 16 may be provided with a filling port, instead of a reservoir 20, whereby molten metal can simply be poured into the chamber 14 or 16 as needed. It will be understood that if such a port (not shown) is provided, a suitable seal would also be provided so as to allow the chambers to be pressurized as discussed above.
  • pressurization of the crucible has been effected by means of injection of a pressurizing gas.
  • a pressurizing gas any other pressurizing means can be used to achieve the same purpose.
  • a mechanical plunger may be used to force the molten metal in the pressurizing chamber 14 to enter the foaming chamber 16 and, thereby, fill the mould cavity.
  • Other such pressurizing means will be apparent to persons skilled in the art.
  • the apparatus and method have focussed on a single mould.
  • the crucible can be provided with multiple moulds and associated gas injection nozzles whereby multiple foam articles can be manufactured concurrently.
  • the crucible 10a comprises a single crucible or furnace with only one chamber 60.
  • the chamber preferably includes a concave bottom as will be described below.
  • the crucible 10a is provided with an upwardly extending neck or foaming chamber 62 above which is positioned the mould 36a.
  • the mould 36a is provided with a supporting stage 64 (which may comprise a table or other such surface) to facilitate the opening and closing of the mould. It will be understood that although this type of supporting stage or table can also be provided (although not shown) in the embodiment of Figures 1 to 5.
  • the mould 36a is preferably provided in two halves 38a and 40a, although various other means of sectioning the mould 36a would be apparent to persons skilled in the art.
  • Each of the mould halves 38a and 40a may also be provided with pistons 42a and 44a, respectively, to facilitate movement of the mould halves to and from each other as shown by the arrows.
  • the mould halves can be slidably supported on the stage 64.
  • the mould 36a also includes a mould cavity 34a having the shape of the desired article to be formed.
  • the mould 36a will generally be provided with one or more vents (not shown) to allow air to escape from the mould cavity 34a when being filled as described below.
  • the foaming chamber 62 includes an opening through which the drive shaft 51a for the nozzle 52a is extended. As discussed above, the nozzle 52a is connected to a motor 54a and a pressurized gas source 56a. A seal 53 a is provided to prevent any molten metal from leaking through the opening for the drive shaft 51a. As shown in Figure 7, the gas discharge nozzle 52a is positioned above the starting liquid level of the molten metal 12a.
  • the crucible 10a is provided with a gas filling port 28a with an associated valve 30a as discussed above. The gas filling port 28a serves to inject a pressurizing gas into the crucible 10a.
  • the apparatus of this embodiment further includes a riser tube 66 extending vertically from the foaming chamber 62 to a position close to the concave bottom of the crucible 10a.
  • the tube 66 may be provided with an outwardly flared bottom end 68.
  • the tube 66 provides a conduit for the molten metal in the crucible 10a to travel to and from the mould cavity 34a as will be described further below.
  • Figure 7 illustrates the starting position of the apparatus when the foaming process is to begin. At this point, the liquid molten metal level in the crucible 10a and the tube 66 is equilibrated and the level in the tube 66 is below the nozzle 52a.
  • the first step in the process involves pressurization of the crucible 10a. This is accomplished by injecting a pressurizing gas through the gas port 28a.
  • the gas supplied to the port 28a may be from any source as known in the art and, as mentioned above, may comprise the same source as that for the nozzle 52a.
  • the mould will include a suitable vent to allow venting of any gases during filling of the mould cavity by the molten metal.
  • Figure 9 illustrates the next step in the process wherein gas is injected into the molten metal contained in the foaming chamber 62 of the apparatus forming bubbles of the gas within the liquid.
  • the bubbles rise into the mould cavity 34a and, as described above in relation to another embodiment, displace the molten metal contained therein.
  • the bubbles accumulate in the mould cavity 34a as a metal foam.
  • the time required to fill the mould cavity with the molten metal and the delay between the filling of the cavity and the initiation of the foaming gas is generally minimised and will vary based on a number of factors.
  • the pressure within the crucible 10a is maintained so as to keep the tube 66 filled with molten metal.
  • Figure 10 illustrates the mould cavity 34a after it is filled with a foam of the metal.
  • the foam in the mould cavity 34a is provided some time to cool and harden to a point where the foam is retained within the cavity.
  • the gas supply to the nozzle 52a is then switched off and the valve 30a is opened to release the pressure accumulated in the crucible 10a.
  • the crucible 10a will include either a molten metal filling port, a molten metal reservoir, or any other means to supply molten metal, as described above for replenishing molten metal consumed during the process.
  • the crucible illustrated in Figures 7 to 11 can be provided with multiple moulds whereby multiple foam articles can be manufactured concurrently.
  • the apparatus of Figures 7 to 11 is shown with one gas discharge impeller, the apparatus may include several such impellers so as to decrease the filling time of the mould.
  • the apparatus of, for example, Figures 7 to 11 may be modular in design by having one or more of the mould 36a, the foaming chamber 62, and the melt chamber 60 releasably secured to one another.
  • any combination of these components can be separated and interchanged without a significant disruption to the process.
  • this would allow, for example, the foaming chamber to be replaced with a new chamber, including an impeller, in cases where the original foaming chamber is malfunctioning or otherwise requires servicing. This may occur, for example, when an impeller becomes obstructed (or clogged).
  • the foaming and casting processes used with the apparatus of Figures 12 to 19 are essentially the same as that for the previously described figures.
  • such an interchangeable apparatus allows the mould and/or casting chamber, to be easily replaced as well.
  • Such change of moulds may be required where, for example, a mould becomes fouled or where a different shaped mould is required in situations where differently shaped articles are required to be formed.
  • one mould can be interchanged for another by simply disconnecting the mould 36a from the foaming chamber 62 and replacing it with a new mould.
  • the modular nature of the apparatus allows such replacement to take place without emptying or otherwise disturbing the crucible 10a.
  • a modular design of the apparatus offers various advantages. Included in these advantages is the ability of a mould and foaming chamber combination to be mounted on known low pressure casting crucibles. As will be understood, this allows avoids the need for any specially designed crucibles.
  • This aspect of the apparatus is illustrated more clearly in Figure 12 where elements common with previously described figures are identified with common reference numerals but with the letter "b" added for clarity.
  • a crucible 10b is provided within a furnace 70.
  • the furnace 70 is provided with heating elements 72 to provide the necessary heat to maintain the metal contained in the crucible 10b in a molten state.
  • the walls of the furnace 70 are made with materials that are capable of withstanding the heat required for the crucible and also with any required insulation.
  • the crucible 10b and furnace 70 may, as described above, be those used for commonly known casting operations.
  • a cover plate 74 is provided over the opening 76 of the crucible 10b.
  • the opening 76 will be circular.
  • the cover plate 74 is provided in the form of an annular disk, the outer diameter of which is larger than the diameter of the opening 76 thereby allowing the cover plate 74 to rest on the upper end of the crucible 10b or furnace 70.
  • a riser tube 66b is secured to the cover plate 74 and extends generally vertically through the inner diameter of thereof.
  • the upper end of the riser tube 66b is provided with a flange 78 having a diameter greater than the inner diameter of the annular cover plate 74.
  • the riser tube is suspended by the flange 78 contacting the upper surface of the cover plate 74.
  • the riser tube 66b is then secured to the cover plate 74 with bolts 80 that extend through apertures (not shown) provided in both the flange 78 and cover plate 74.
  • the crucible may also be provided with a pressurizing means such as described herein to cause the molten metal to rise through the riser tube 66b.
  • Figure 12 shows the riser tube 66b filled with molten metal 12b.
  • a guide 82 is provided above the riser tube 66b and may also be secured to the cover plate 74.
  • the guide 82 includes a lower opening 84 that generally corresponds to the upper opening of the riser tube 66b and, optionally, a tapered upper end that terminates in an upper opening 86.
  • the upper opening 86 serves to feed molten metal 12b into a foaming chamber 62b.
  • the foaming chamber 62b is supported on a support plate 88 which, in turn, may rest on a stage 90.
  • the base of the foaming chamber 62b is provided with an opening that allows fluid communication with the upper opening 86 of the riser tube 66b.
  • the foaming chamber 62b is provided with one or more gas discharge nozzles 52b.
  • Figure 12 illustrates for convenience one nozzle 52b but it will be appreciated by persons skilled in the art that additional nozzles may also be provided in the foaming chamber 62b.
  • the nozzle 52b serves to introduce a foaming gas into the molten metal contained in the foaming chamber 62b thereby forming the metal foam.
  • the level of the molten metal is raised above that of the nozzle 52b when foaming is to commence.
  • Figure 12 illustrates a stage in the process where foaming is not commenced, wherein the level of the molten metal 12b is below the nozzle 52b.
  • the upper end of the foaming chamber is provided with an opening 32b through which the generated foam is passed into the mould or casting chamber 36b.
  • the mould 36b may be preferably provided above the foaming chamber 62b to facilitate entry of foam.
  • Figure 12 also illustrates a preferred structure of the foaming chamber 62b wherein the chamber is provided in two sections - a top section or foaming box 92 and a bottom section or feeder box 94.
  • the feeder box 94 receives molten metal from the riser tube 66b.
  • the nozzle 52b is connected to the foaming box and, when foaming is required, the level of the molten metal in the foaming chamber 62b is raised (as described herein) so that molten metal is caused to enter the foaming box 92, thereby submerging the nozzle 52b. It will be understood that dividing the foaming chamber 62b into sections allows for ease of access for servicing or maintenance functions.
  • the foaming chamber 62b and the mould 36b are separate modules that are combined with the crucible 10b to form the apparatus of the invention.
  • such modularity allows either of the components to be easily removed and replaced with minimal interruption to the process.
  • another feature of the modular design of the foaming apparatus described herein lies in the fact that various components of the apparatus may be removed and serviced or changed without moving the crucible. The advantage in this case being that heavy and/or hot components need not be manipulated.
  • Figure 13 illustrates another aspect of the apparatus of Figure 12 and serves to illustrate the interchangeability of the modules of the apparatus.
  • Figure 13 illustrates an embodiment of the apparatus of Figure 12 wherein the single cavity mould 36b is replaced with a multiple cavity mould 36c. As shown, the crucible 10b and riser tube 66b are the same as that of Figure 12. However, the foaming chamber 62c illustrated in Figure 13 is provided with multiple (i.e. more than one) gas discharge nozzles 52c, which are preferably positioned below multiple (i.e. more than one) upper openings 32c provided on the foaming chamber 62c.
  • the mould 36c of this embodiment also includes multiple cavities each having an entry port in fluid communication with the openings 32c of the foaming chamber 62c.
  • the embodiment of Figure 13 is illustrated with a mould having three similarly shaped cavities, it will be appreciated that this is only by way of example and that any number or shape of cavities may equally be provided.
  • one or more nozzles may be used with a suitable manifold or diverter to direct molten metal and/or foam into the appropriate cavities of the mould.
  • FIG. 17 An example of multiple nozzles being provided in a foaming chamber is illustrated in Figure 17, where like reference numerals are used but with the letter "f ' added for clarity.
  • multiple nozzles 52f are provided within a foaming chamber wherein each nozzle is arranged below an opening into the mould. It will be appreciated that such arrangement serves to increase the speed of foam generation and, therefore, the casting process.
  • Each of nozzles 52f may be associated with one or more gas sources 56f. As discussed above, the nozzles 52f may also be connected to one or more drive motors to cause rotation of same.
  • any number of foaming chambers and/or casting chambers or moulds may be used with the invention.
  • multiple foaming chambers can be associated with a single pressurizing chamber.
  • Each of the foaming chamber can, in turn, be associated with multiple casting chambers.
  • the apparatus of the invention can be optimized or tailored as needed in order to simultaneously form multiple articles or various forms and at various speeds.
  • various foaming and casting chambers it would be possible for various articles (of the same or different shape) to be formed with one pressurization cycle.
  • the process followed by the apparatus of Figures 12 and 13 is essentially the same as that described herein with respect to other figures.
  • Figures 14 to 16 illustrate a further aspect of the invention wherein a vacuum source is used to supplement the pressure feed system for the molten metal.
  • Figures 14 to 16 are similar to the embodiment of the invention illustrated in Figures 1 to 6.
  • the reference numerals used in Figures 1 to 6 are also used in Figures 14 to 16 but with the letter "d" added for convenience.
  • the apparatus includes a pressurizing chamber 14d and a foaming chamber 16d, which are in fluid communication by means of a channel 19d.
  • the apparatus also includes a mould 36d having a mould cavity 34d.
  • the pressurization and foaming chambers, the channel and the mould are preferably formed with thick insulative walls so as to conserve heat within the apparatus and thereby prevent or minimize the molten metal from solidifying.
  • the pressurizing chamber 14d contains a volume of molten metal 12d.
  • the channel 19d allows the molten metal 12d to freely flow between the pressurization and foaming chambers 14d and 16d, respectively.
  • the foaming chamber 16d includes at least one gas discharge nozzle 52d connected to a gas source (not shown).
  • the pressurizing chamber 14d includes a gas introduction port 28d connected to a source of pressurized gas (not shown). However, according to the embodiment illustrated, the pressurizing chamber is also provided with a vacuum port 96 connected to a vacuum source (not shown). Further, the mould 36d of this embodiment also includes a vacuum port 98 connected to a vacuum source (not shown).
  • the apparatus of Figures 14 to 16 functions similarly to that of Figures 1 to 6.
  • the level of molten metal in the foaming chamber 16d is raised until the gas discharge nozzle 52d is submerged at which point gas is discharged through the impeller 52d thereby causing the molten metal to foam.
  • the method of raising the molten metal level is slightly different from the previous embodiment.
  • the starting position of the apparatus is illustrated in Figure 14 wherein the molten metal level is maintained below the level of the nozzle 52d. This is achieved by avoiding pressurization of the chamber 14d but, instead, engaging the vacuum source and causing a vacuum (or negative pressure) to be developed in chamber 14d through the vacuum port 96.
  • FIG. 15 illustrates the next step in the process wherein the vacuum source for the pressurizing chamber 14d is released while the vacuum source, connected to the vacuum port 98 of the mould 36d is engaged. In addition, the pressure within the pressurizing chamber 14d is increased by injecting the pressurizing gas through the port 28d.
  • FIG. 15 illustrates the apparatus wherein both vacuum ports 96 and 98 are in the "off position and where the pressurized gas port 28d is used to maintain a constant pressure within the pressurizing chamber 14d.
  • Figure 15 illustrates an embodiment wherein the foaming operation is commenced as soon as the nozzle 52d is submerged by the rising molten metal level. At such point, the gas supply to the nozzle is turned on thereby resulting in the generation of the foam. The foam then rises into the mould cavity 34d and fills same. Gas supply to the nozzle 52d is turned off when a sufficient volume of foam is generated, specifically, when the mould cavity 34d is filled.
  • the molten metal level may be increased until the mould cavity 34d is filled with molten metal prior to the foaming operation.
  • a vacuum source is used to assist the pressurizing system in adjusting the level of molten metal within the pressurization and foaming chambers.
  • flow assistance can be provided by using an object (not shown) that can be raised and lowered within the molten metal contained in the pressurizing chamber 14d. It will be understood that such object will be made of a material capable of withstanding the heat of the molten metal.
  • the pressurizing chamber will be understood as having no other means of egress for the molten metal except into the foaming chamber or, alternatively, the route for the melt into the foaming chamber offers the least resistance to flow. In the latter case, it will be understood that molten metal, once displaced by the object, will preferentially flow into the foaming chamber.
  • the molten metal level can be adjusted by means of a pump connected to a separate molten metal tank.
  • a furnace 100 serves as a source of molten metal 12e that is fed into a foaming chamber 16e.
  • the furnace 100 will be provided with suitable heating elements (not shown) to maintain the metal in the molten state and, if necessary, to melt any solid metal provided therein.
  • the furnace may optionally be provided with a mixer 24e to stir the molten metal.
  • the furnace is provided with at least one of each of entry and exit ports 104 and 106, respectively, through which the molten metal is allowed to flow.
  • the foaming chamber 16e is also provided with entry and exit ports 108 and 110, respectively.
  • the exit port 106 of the furnace 100 is fluidly connected to the entry port 108 of the foaming chamber 16e.
  • the exit port 110 of the foaming chamber 16e is fluidly connected to the entry port 104 of the furnace 100.
  • the fluid connections are provided by suitable conduits 112 and 114, respectively, as will be known in the art.
  • Each of the conduits 112 and 114 include at least one pump 116 and 118, respectively, for pumping molten metal there-through.
  • the pumps 116 and 118 are operable independently of one another and, therefore, by operating one pump at a higher speed (i.e. flow rate) than the other, the molten metal volume in each of the furnace 100 and the foaming chamber 16e can be adjusted.
  • the level of the molten metal 12e in the foaming chamber 16e can be increased by operating pumps 116 and 118 so as to increase the flow rate of molten metal into the foaming chamber 16e as compared to the flow rate entering the furnace 100.
  • the speed of the pumps will vary depending on their capacities, the cross sectional area of the conduits, 112 and 114, and the dimension of the openings for ports 104, 106, 108 and 110.
  • the pumps 116 and 118 can be used to circulate molten metal 12e and cause mixing thereof. Such an arrangement would avoid the need for mixers and the like to cause mixing of the molten metal.
  • the foaming chamber can be provided with one or more nozzles 52e for introducing a gas into the molten metal 12e thereby generating the required foam.
  • the foam can then be directed into one or more moulds (not shown).
  • a hood 5Oe or other such diverter can be used to direct the foam into the mould or moulds.
  • one of the pumps 116, 118 can be removed and the flow of molten metal can be achieved with only one pump.
  • a return flow of molten metal where needed, can be established with a conduit alone and that such return flow could be powered by gravity.
  • the circulating flow of molten metal flow as established in the apparatus of Figure 18 also serves to maintain a generally constant temperature of the molten metal in both the furnace and the foaming chamber. It will be understood that the furnace 100 of Figure 18 is functionally equivalent to the pressurizing chambers described above.
  • any one or a combination of pressure, vacuum, displacement objects, pumps, or any other similar means can be used to adjust the molten metal level within the chambers of the apparatus of the invention and that any of these means can be used in any of the embodiments discussed herein. All these means serve to control the level of molten metal in the various chambers.
  • the apparatus includes a pressurizing chamber 14g, a foaming chamber 16g and a casting chamber or mould 36g.
  • the pressurizing chamber 14g and foaming chamber 16g are connected by a channel 19g, which allows molten metal 12g to flow between the two chambers.
  • the foaming chamber 16g is provided with one or more gas discharge nozzles 52g, which are connected to a gas source 56g.
  • the nozzles 52g may also be rotatable by means of a motor (not shown).
  • the pressurizing chamber 14g is provided with a gas port 28g through which is injected a pressurizing gas as described above. Foaming in the foaming chamber 16g is accomplished in the manner described above.
  • the level of molten metal in the foaming chamber 16g is increased until the gas discharge nozzles 52g are submerged. At such time, the gas supply to the nozzles 52g is actuated thereby causing foaming of the molten metal 12g.
  • the foaming chamber 16g and casting chamber 36g are connected by means of a transfer channel 120, which serves to transfer foam generated in the foaming chamber 16g to the mould cavity 34g in the casting chamber or mould 36g. It will be understood that the components of the apparatus, including the transfer channel 120 will be provided with any required insulation or heating means to prevent undesired solidification of foam and/or molten metal in areas apart from the mould cavity.
  • foam can be pushed into the mould cavity 34g by continuing the foaming operation.
  • the continuously generated foam fills the transfer channel 120 and subsequently enters the mould cavity 34g.
  • one of the advantages of an apparatus incorporating a transfer channel 120 lies in the fact that the casting chamber or mould 36g need not be located above the foaming chamber.
  • a standard sand mould can be used wherein the mould sections 38g and 4Og are located above one another.
  • the sand incorporating the mould cavity 34g can be contained in the lower section of the mould.
  • the pressurizing chamber 14g of Figure 18 can be associated with more than one foaming chamber in the manner described above. Further, the flow of molten metal between the pressurizing chamber and foaming chamber can be accomplished using any of the means discussed above.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Continuous Casting (AREA)

Abstract

L’invention porte sur un appareil de coulage d’un article de mousse métallique comprenant un creuset pour contenir le métal en fusion, une buse d’injection de gaz située au-dessus du niveau du métal en fusion, au niveau neutre, et un moule ayant une cavité de moule de la forme de l’article. L’appareil comporte un moyen pour relever le niveau du métal en fusion au-dessus de la buse d’injection de gaz pour générer la mousse. Un procédé de coulage de l’article en mousse consiste à maintenir le niveau du métal en fusion au-dessous de la buse d’injection de gaz jusqu’à ce que l’on souhaite créer une mousse, à relever le niveau du métal en fusion au-dessus de la buse d’injection de gaz et à injecter un gaz dans le métal en fusion pour générer la mousse de métal. Le procédé consiste également à diriger la mousse dans le moule et à la refroidir pour former l’article de mousse. L’appareil peut être constitué de modules séparables permettant ainsi d’adapter le processus pour répondre à des exigences spécifiques.
PCT/CA2005/001278 2004-08-24 2005-08-24 Appareil de coulage de mousse métallique et procédés idoines WO2006021082A1 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008034436A1 (fr) * 2006-09-22 2008-03-27 Kurtz Gmbh Dispositif de coulée pour la fabrication de structures de mousse à pores ouverts à partir de métal, d'alliages métalliques, de matière plastique ou de céramique avec ou sans enveloppe extérieure fermée
US7699092B2 (en) 2007-06-18 2010-04-20 Husky Injection Molding Systems Ltd. Metal-molding system and process for making foamed alloy
WO2010064059A3 (fr) * 2008-12-04 2010-07-29 Bay Zoltán Alkalmazott Kutatási Közalapítvány Procédé de production d'une mousse métallique au moyen d'oscillations et produit en mousse métallique ainsi obtenu
EP2502688A1 (fr) * 2011-03-23 2012-09-26 ADMATIS Kft. Appareil et procédé de production de produits en mousse métallique formée, à cellules fermées, stabilisés par des particules avec un injecteur de mousse métallique
WO2013144881A2 (fr) 2012-03-27 2013-10-03 Universidade Do Minho Structure métallique légère et procédé de production respectif

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Publication number Priority date Publication date Assignee Title
US5865237A (en) * 1996-04-19 1999-02-02 Leichtmetallguss-Kokillenbau-Werk Illichmann Gmbh Method of producing molded bodies of a metal foam
CA2440488A1 (fr) * 2002-09-09 2004-03-09 Huette Klein-Reichenbach Gesellschaft M.B.H. Procede et dispositif pour la fabrication de mousse metallique a ecoulement fluide
CA2445660A1 (fr) * 2002-11-18 2004-05-18 General Motors Corporation Methode de fabrication de metal a alveoles fermes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5865237A (en) * 1996-04-19 1999-02-02 Leichtmetallguss-Kokillenbau-Werk Illichmann Gmbh Method of producing molded bodies of a metal foam
CA2440488A1 (fr) * 2002-09-09 2004-03-09 Huette Klein-Reichenbach Gesellschaft M.B.H. Procede et dispositif pour la fabrication de mousse metallique a ecoulement fluide
CA2445660A1 (fr) * 2002-11-18 2004-05-18 General Motors Corporation Methode de fabrication de metal a alveoles fermes

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008034436A1 (fr) * 2006-09-22 2008-03-27 Kurtz Gmbh Dispositif de coulée pour la fabrication de structures de mousse à pores ouverts à partir de métal, d'alliages métalliques, de matière plastique ou de céramique avec ou sans enveloppe extérieure fermée
US7699092B2 (en) 2007-06-18 2010-04-20 Husky Injection Molding Systems Ltd. Metal-molding system and process for making foamed alloy
WO2010064059A3 (fr) * 2008-12-04 2010-07-29 Bay Zoltán Alkalmazott Kutatási Közalapítvány Procédé de production d'une mousse métallique au moyen d'oscillations et produit en mousse métallique ainsi obtenu
CN102307687A (zh) * 2008-12-04 2012-01-04 贝佐尔坦应用研究基金会 通过振动制造泡沫金属的方法及由此获得的泡沫金属产品
US9168584B2 (en) 2008-12-04 2015-10-27 Bay Zoltan Alkalmazott Kutatasi Kozhasznu Nonprofit Kft. Method of producing a metal foam by oscillations and thus obtained metal foam product
EP2502688A1 (fr) * 2011-03-23 2012-09-26 ADMATIS Kft. Appareil et procédé de production de produits en mousse métallique formée, à cellules fermées, stabilisés par des particules avec un injecteur de mousse métallique
WO2013144881A2 (fr) 2012-03-27 2013-10-03 Universidade Do Minho Structure métallique légère et procédé de production respectif

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